The present invention relates to a disk cartridge comprising a hard casing in which a magnetic disk is contained in a rotatable manner.
A floppy disk has widely been used as an exchangeable information storage medium which can be mounted on a driving unit and removed from it for storage and transportation in the same manner as a magnetic tape cassette or a disk pack.
Especially, a small-sized floppy disk, which is smaller than an ordinary floppy disk, is commonly used for personal computers because of an economical price. In this type of floppy disk, a thin flexible jacket is used as a casing to protect a magnetic disk. The thin flexible jacket is, however, insufficient to protect the magnetic disk. On account of this, there is proposed a disk cartridge in which a magnetic disk is rotatably contained in a thick, undeformable, strong, hard casing whose inner surfaces are attached with lining sheets.
FIG. 1 is a longitudinal cross-sectional view showing the above-mentioned disk cartridge being mounted on the driving unit. In FIG. 1, a reference numeral 10 designates an upper hard casing; a numeral 12 designates a lower hard casing and a numeral 14 designates a magnetic disk. The magnetic disk 14 is rotatably contained in the upper and lower hard casings 10, 12 whose inner surfaces are bonded with lining sheets (not shown). The magnetic disk 14 comprises a circular plate-like magnetic sheet 16 and a hub 18 at the central part of the magnetic sheet 16. The hub 18 is made of metal and comprises a central circular recess 20 as the major part and an annular part 22 extending from the outer periphery of the circular recess 20. In the central part of the inner surface of the upper hard casing 10, there is formed an annular pojection 24. The free end portion of the annular projection extends in the circular recess 20 of the hub to restrict a region of rotation of the magnetic disk 14.
When the disk cartridge is mounted on the driving unit, a driving pin 26 of the driving unit is inserted into the central opening of the hub 18 and the top end of the pin reaches a bearing part 28 positioned in the central portion of the upper hard casing 10, whereby the magnetic disk 14 is suspended in the upper and lower hard casings 10, 12 to be in a freely rotatable condition. In FIG. 1, numerals 30, 32 respectively designate supporters upwardly extending from the driving unit to support the disk cartridge.
However, when the disk cartridge having the construction as above-mentioned is mounted on the driving unit, it is inavoidable that the hub 18 is pushed up by the driving pin 26, whereby the hub 18 temporarily comes in contact with the inner surface of the upper hard casing 10. Further, the driving unit is generally provided with two driving pins 26 to enhance accuracy in driving operation: one enters the central opening of the hub 18 and the other enters another opening. Though it is easy to insert the driving pin into the central opening, insertion of the other driving pin into the other opening is not easy, on account of which the top end of the other driving pin 26 pushes up the hub 18 until it enters the other opening. When the hub 18 is raised, it is brought into contact with the inner surface of the upper hard casing 10. If they repeatedly come in contact with each other, the inner surface of the upper hard casing 10 is shaved by the hub to produce powder from the casing. Particularly, production of powder is notable when the hub 18 is made of metal and the upper hard casing 10 is made of resinous material. The shaved powder is harmful to operation. When the powder is deposited on the surface of the magnetic sheet 16, there results an adverse affect on operation of the magnetic disk and in the worst case, it becomes inoperative.